Telephone-circuit



(NoMocieL) H. S. THORNBERRY.

TELEPHONE CIRCUIT. No. 320,414. Patented June 16, 1885.

N. PETER5. Phuto Lilhogrzpbar. Wa-hin tnn. 0.6.

of which the following is a specification.

. UNITED STATES HENRY S. THORNBERRY, OF

PATENT OFFICE.

BOSTON, MASSACHUSETTS.

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 320,414, dated June 16, 1885.

Applicatioufiled November 20, 1884.

To aZZ whom, it may concern.-

Be it known that I, HENRY S. THORN- BERRY, of Boston, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in TelephoneOircuits,

The object of my invention is to'obviate the evil effects of inductive and other similar disturbances on telephone-lines.

It is well known that when two electrical conductors are placed in proximity sudden variations of the electrical condition in one will produce variations in the other, more or less pronounced, according to the nature of such variations and the proximity of the two conductors in question. The effect of this action of one current upon another is very apparent in telephonic instruments, and to obviate the ill effects thereof resort is had to the use of a complete metallic circuit, wherein the telephone-instruments are placed. I have discovered that in using such circuits between points widely separated the two terminal stations can communicate much more freely and uninterruptedl y if no intermediate stations are in circuit; or, to state the fact in other words, it has been found that the introduction of instruments at stations intermediate between the terminal stations operates to render apparent such interfering and troublesome electrical effects as the use of the metallic circuit is calculated to avoid. This seems to be due to the disturbance of the electrical balance existing between the two sides of the metallic loop, caused by the introduction of a resistance and the production of an electrical effect (as the magneto-electric inductive) in one side of the metallic circuit or loop only, and my invention is designed to remedy this difficulty.

In another application heretofore filed I have described and claimed a method of obviating inductive or disturbing effects in a metallic circuit, which consisted in producing andmaintainin g an electrical balance between the two sides of such circuit by introducing into one side of said loop or circuit means to compensate or balance the effect produced by the introduction of the telephone and accompanying instruments in the other side. This could be accomplished by using two telephone sets, substantially alike in their construction, t

(No model.)

and placing one set in each side of the metallic circuit at the intermediate station.

My present invention is an iin 'novement. upon the means for practicing the invention described in my former application; andit consists in a telephone and transmitter the coils of which are arranged for simultaneous insertion with respect to both sides of the loop or circuit, whereby the resistance and the electrical effect caused by the insertion of such telephone or telephones is equally distributed between the two sides of the circuit or loop. For this purpose I divide the coils or helices of the telephones into two equal sections, and place one section in each side of the circuit, arranging the connections so that the electrical current will pass through both sides in the same direction, causing both sections to contribute to the same result.

The accompanying drawing illustrates my invention.

A and B are two stations connected by a metallic circuit. 0 is an intermediate station provided with receiving and transmitting telephones T t, of any ordinary form. The coils, however, of the telephone T and the inductioncoil I are arranged in two sections or divisions, 0 c i 22. One of each section, as c and 'i, is placed in one side of the circuit; the other sections, 0 and t", are placed in the opposite side of the circuit. The connections are so arranged that an electrical impulse passing through the sections a and i in a given direction-on, say, the first side of the circuit and returning in the second side-will pass through the sections 0 and i in the same direction as it did through sections 0 and i.

The bell or ringer R, or an annnnciator,'is used as an alarm to attract attention when the station is wanted, and replaces the telephones when they are not in use. The coil of this indicatinginstrument is divided into two equal sections, and the electrical connections are so arranged, as in the case of the telephones, that the electrical current will pass through both sections in a direction calculated to produce the same effect.

By the means described the disturbances of the electrical balance caused by the insertion of an instrument in one side of the circuit only is avoided.

1 am aware that it has been heretofore proposed to overcome the effects of induced currents upon a receiving-telephone placed in a grounded circuit by means of a so-called compensating-circuit running parallel there with, and exposed to the same disturbing influences, the wire of said compensating-circuit being coiled around the core of thereceivingtelephones magnet in a direction opposite to that of the maincircuit wire. Such arrangement is not within the scope of my invention.

WVhat I claim is- 1. The combination of a telephone having a coil in two sections and a metallic circuit, in the opposite sides of which the said coil sections are respectively placed.

2. The combination of a metallic circuit and. an electro-magnet having a coil in two sections, respectively located in opposite sides of said circuit.

0. The combination of a metallic circuit and an inductorium, the secondary coil of which is divided into two equal sections included in opposite sides of the said circuit, respectively. 4. The combination of a receiving-telephone having a coil or helix divided into two equal sections, an inductorium, the secondary coil of which is composed of two equal sections, and a metallic circuit, the opposite sides of which respectively include one section of coil of each of said instruments.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 18th day of November, 1884.

H. S. THORNBERRY. \Vitnesses:

WM. B. VANSIZE, GEO. WILLIs PIERCE. 

